水位变化下长江下游围垦集约养殖鱼塘消落带温室气体排放影响机制:以南京地区为例

The impact mechanism of greenhouse gas emissions in the dissipation zone of intensive farming fish ponds under water level changes in the lower Yangtze River:a case study of the Nanjing area

为了研究水位变化对淡水养殖鱼塘消落带沉积物温室气体(GHGs)排放的影响,结合前期野外观测数据,选取南京市温室气体高排放的养殖鱼塘消落带沉积物为研究对象,通过室内微宇宙培养实验,设置高水位、低水位、先高后低和先低后高4个不同水位的处理组,并结合气相色谱法、紫外-可见光光谱法和三维荧光光谱技术(3D-EEMs)等方法探讨其影响机制。结果表明:静态高水位组的CH_(4)累积排放量是静态低水位组的3.46倍,静态低水位组的CO_(2)累积排放量是静态高水位组的1.21倍,静态低水位组的N_(2)O表现为持续吸收。动态组中,水位上升和下降均促进了CO_(2)、CH_(4)和N_(2)O的排放,其中水位上升组的CO_(2)和CH_(4)累积排放量分别是静态低水位组的1.15倍和2.53倍,水位下降组CO_(2)、CH_(4)和N_(2)O累积排放量分别是静态高水位组的1.25、1.08倍和2.84倍。研究表明:水位变化差异和变化影响下的消落带沉积物溶解性有机质对温室气体的产生和排放起到了关键作用。CO_(2)排放与可溶性有机碳浓度相关性最高。CH_(4)排放与C/N呈显著负相关关系,同时与溶解性有机质定性光谱指数[腐殖化指数(HIX)和SUVA254(254 nm波长处的紫外吸光度与总有机碳的比例)]有显著相关关系。N_(2)O的排放主要受水位变化引起的硝化与反硝化作用的影响。

The sediment in the aquaculture fish ponds with high greenhouse gas emissions,combined with previous field observation data,was studied to determine the impact of water level changes on greenhouse gas(GHGs)emissions from sediment in freshwater aquaculture fish ponds in Nanjing.Through indoor microcosm cultivation experiments,four different water level treatment groups were set up:high,low,high then low,and low then high.Gas chromatography was also used.Influencing mechanisms were explored using UV visible spectroscopy and 3D fluorescence spectroscopy(3D-EEMs).Research has shown that:the CH_(4) emission capacity of the static high water level group are 3.46 times that of the static low water level group.The cumulative CO_(2) emissions of the static low water level group are 1.21 times that of the static high water level group.The static low water level group shows continuous absorption of N_(2)O.The data of the dynamic simulation group shows that both rainstorm and sudden drought promote CO_(2) and CH_(4) emissions,and the cumulative emissions of these gases in the simulated rainstorm group are 1.15 times and 2.53 times,of the static low water level group respectively.The cumulative CO_(2),CH_(4),and N_(2)O emissions in the simulated drought group were 1.25 times,1.08 times,and 2.84 times higher than those in the static high water level group,respectively.Research has shown that the differences and effects of water level changes in soluble organic matter play a crucial role in the production and emission of GHGs.The correlation between CO_(2) emissions and soluble organic carbon concentration is highest.There is a significant negative correlation between CH_(4) emissions and C/N,as well as a significant correlation with dissolved organic matter qualitative spectral indices(HIX and SUVA254).N_(2)O emission is mainly affected by nitrification and denitrification caused by changes in water level.